Project 4: Bioenergetics, metabolism, and lifespan in p66Shc(-/-) mice The mechanism for life span extension in p66Shc(-/-) mice is not known. However, the fact that body weight and mitochondrial reactive oxygen species (ROS) production are altered in these mice suggest that changes in energy metabolism may be a central mechanism contributing to the retardation of aging in these animals. Body composition and the activities of some enzymes of intermediary metabolism are also changed in p66Shc(-/-) mice when compared to wild-type controls, and this further supports the idea that energy intake and/or expenditure are altered in p66Shc(-/-) mice. Energy metabolism has long been considered to play a central role in the aging process, and the purpose of Project 4 is to determine if components of energy metabolism are altered in the p66Shc(-/-) mice. The rate of living theory would predict that increased longevity in the p66Shc(-/-) mice should be associated with a decrease in energy metabolism. Since energy metabolism appears to play a role in both aging and ROS production, it is important to test the hypothesis that energy metabolism is reduced in p66Shc(-/-) mice vs controls. To properly determine the effect of p66Shc on energy metabolism, whole animal, mitochondrial, and biochemical measurements will be completed. We propose four specific aims to determine the effect of p66Shc on energy metabolism: Specific Aim 1: To determine whole animal 24-hour and resting energy expenditure in p66Shc(-/-) and wild-type mice using indirect respiration calorimetry. Specific Aim 2: To determine mitochondrial proton leak kinetics in heart, liver and skeletal muscle mitochondria from p66Shc(-/-) and control mice. Specific Aim 3: To determine the activity of enzymes that control flux through major energy metabolism pathways in heart, liver and skeletal muscle of p66Shc(-/-) and control mice. Specific Aim 4: To determine lifespan under barrier conditions in ad libitum fed and 40% calorie restricted p66Shc(-/-), p66Shc(+/-) and wild-type mice. Relevance to public health: These studies will increase our knowledge about the effects of p66Shc on energy metabolism, ROS production and life span;therefore/the elucidation of the role p66Shc in lifespan extension will likely be relevant to human health in the United States.